Question

How can I set a digit in a hexadecimal number?
I currently have this code:

int row = 0x00000000;
row |= 0x3 << 8;
row |= 0x2 << 4;
row |= 0x1 << 0;

printf("Row: 0x%08x", row);

Which works perfectly fine as long as “row” is just zeros. As soon as I change it to something like this:

int row = 0x33333333;
row |= 0x3 << 8;
row |= 0x2 << 4;
row |= 0x1 << 0;

printf("Row: 0x%08x", row);

I just get this output:

Row: 0x33333333

Answer 1

You should delete (make it 0) the digit first.

row &= ~(0xf << 4);

~ operator reverses the values of all bits in the number. So. 0x000000f0 becomes 0xffffff0f.

Your code should look like:

row &= ~(0xf << 8);
row |= 0x3 << 8;
row &= ~(0xf << 4);
row |= 0x2 << 4;
row &= ~(0xf << 0);
row |= 0x1 << 0;